Water distributing devices, such as fixed sprayers used for irrigation purposes, are limited in respect to the distances at which spray patterns can be discharged. Further, conventional sprayers are incapable of functioning in the desired manner when they are supplied with water at relatively low mainline pressures, such as below 25 psi. Thus, conventional sprayers and other water distributing devices cannot be retro-fitted to systems working under marginal pressure levels provided by existing pumps, mainlines, and sub-mainline infrastructures. The alternative to converting marginal systems of this type to include pumps or other accessories for boosting pressures to an acceptable working level, would be cost prohibitive and impracticable.
A proposed solution to these problems has been the advent of pulsating devices, adapted to discharge water from an irrigation sprayer at greater distances then can be achieved with conventional sprayers. For example, U.S. Pat. No. 4,301,967 discloses a pulsating-type sprinkler system wherein an elastomeric tube or bladder intermittently expands and contracts to control the opening and closing, respectively, of a valve to discharge water in intermittent pulses. U.S. Pat. No. 4,781,217 discloses a pulsating-type irrigation system that relies on an expandable (FIG. 1) or fixed volume container (FIG. 4) for receiving fluid via a fixed orifice to provide intermittent pulses of water under control of a spring-biased and separate check valve. U.S. Pat. No. 4,955,539 discloses a similar system wherein a rigid container is utilized to receive pressure-compensated water and thereafter discharge the water in intermittent pulses under the control of a pre-set check valve comprising an expansible elastomeric sleeve.
Pulsating devices of the type described above must necessarily function within very narrow flow and line pressure ranges to be practicable. Further, such systems are normally incapable of operating efficiently at relatively low line pressures, e.g., below 25 psi. In addition, the systems are prone to one or more of the following problems: Inconsistent start-up to initiate a pulsating cycle; utilization of discharge orifices having different sizes that properly function at varied flow rates, even within narrow ranges; a tendency to randomly stop or emit a steady (non-intermittent) stream of water when placed in operation; a tendency to emit a steady stream of water, rather than intermittent pulses, when operated at relatively high flow rates and/or pressures; and inability to continuously and cyclically provide for the uniform discharge of water at regular frequencies.